Let say we have a collection transactions which contains some document and documents contain payments which is array of objects.
Now my task is to get the unique types in payments array of every document.
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{ 'id':'74656345' 'payments':[ { 'amount': 200, 'type': 'Debit Card' }, { 'name': 300, 'type': 'Internet Banking' }, { 'name': 300, 'type': 'Credit Card' } ], }, { 'id':'9783475' 'payments':[ { 'amount': 200, 'type': 'Debit Card' }, { 'name': 300, 'type': 'Internet Banking' }, { 'name': 300, 'type': 'UPI' } ], } |
Expected Result: Debit Card, Internet Banking, Credit Card, UPI
which is unique values of payment types in transctions collection and the MongoDB query for that is given below:
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db.transctions.aggregate( {'$unwind':'$payments'}, {"$group" : {"_id": "$payments.type"}} ) |
Here we first unwind the data so that every payments array can be converted to objects and then we are grouping the type of payments document in transctions collection. ...
